Although excimer lasers cause precise microablation without surrounding thermal tissue injury, the importance of early and late healing responses must be determined prior to safe therapeutic vascular applications. Therefore, normal canine femoral artery segments were exposed to 308nm excimer laser radiation and animals were sacrificed at 2 hours, 2 days, 10 days, and 6 weeks after initial treatment. Perfusion fixed vascular specimens were analyzed by light, scanning, and transmission electron microscopy. At two hours, after laser treatment the endothelium was desquamated and covered by platelets. A smooth monolayer of axially aligned normal endothelial cells was present without surface organizing thrombus by 10 days. At 6 weeks, there were no aneurysms and no important surface hyperplastic responses. Thus, favorable acute and chronic pathologic responses in vascular tissue suggest that the excimer laser is suitable for clinical angioplasty procedures.